In some environments it is important to have a protective and resistant structure to enclose materials (i.e., munitions; chemicals; nuclear waste storage), persons or buildings (control centres; hospitals), the structure able to mitigate or withstand the impact of projectiles such as bombs or shells, or that can otherwise withstand very high dynamic loads, such as cyclic, impactive or impulsive loads.
Such protective structures, known as bunkers, can be portable or fixed. They are often partially or completely buried underground under compacted layers of soil, especially in military settings. In a military setting, portable protective bunkers which are easy to set up at a selected site to enhance the safety of military personnel are very desirable.
As well, larger more permanent bunker structures that can protect ammunition or other explosive or dangerous materials, or that can house entire rooms or buildings to protect them from outside attack are also very desirable.
A portable combat bunker is described in U.S. Pat. No. 6,067,889. This bunker is stated to be portable and reusable, formed of molded hollow plastic modules temporarily joinable by wooden beams and metal brackets. The modules are assembled on site and filled with water or sand, which is drained when the bunker is moved to a new location.
U.S. Pat. No. 6,205,717 describes a bunker construction that is formed of precast concrete arch elements which form a semicircular roof of the bunker, and front and back plates on the ends of the bunker. This bunker is covered with protective earth, thereby allegedly forming a bunker construction with enhanced structural integrity due to the mechanically stabilized earth in combination with the precast arch elements and the front and back plates.
Canadian patent application no. 2,000,436 describes a device for improving the resistance of structures, in particular made of concrete, such as shelters, sheds, building, walls, paved surfaces, to the impact of conventional projectiles such as bombs and shells. The device comprises a surface formed by a succession of ribs and grooves with a substantially V-shaped profile and smooth, inclined lateral faces. These surfaces deflect a projectile after impact, to weaken the impact of the projectile on the structure.
Canadian patent no. 2,438,802 describes a structural system that absorbs impactive and impulsive loads and that comprises a main structure, a crushable filling layer around the main structure and an outer shield around the crushable filling layer. If an impactive load exceeds a certain level, the outer shield slides, crushing the filling layer and absorbing a substantial amount of energy.
What is needed is a better bunker system that can withstand forces that are applied to it to protect persons or property inside the bunker, and one that is easy to set up when being used as a portable bunker system.